Drag shoes are typically utilized by street sweepers to confine dirt, debris, dust, etc., inwardly of a main street sweeping brush. Typically, a drag shoe assembly is mounted to each side of a street sweeper and depends downwardly therefrom adjacent the main sweeping brush or broom. As the brush rotates, dirt, debris, dust, etc., being moved by the brush tends to be confined underneath the sweeper by the drag shoes.
Since the drag shoes must engage the underlying surface being traversed by the sweeper, it follows that it is desirable for the drag shoe to be mounted such that it can float or move up or down over uneven surfaces. This is typically provided by a series of rigid links interconnected between the street sweeper and the drag shoe.
One of the most common problems encountered with street sweepers and drag shoes, results when the street sweeper is being turned or moved laterally and the drag shoe encounters an obstruction such as a manhole cover, street curb, or the like. Typically there is little flexibility built into the linkage interconnecting the drag shoe with the street sweeper's frame structure. Once the obstruction or lateral load is encountered the drag shoe is forced to move laterally. The result is that the drag shoe is often damaged as well as the upper supporting frame structure and the interconnecting linkage arrangement. Also, the impact is such that the drag shoe will not freely return to its initial normal vertical position. The end result is that the drag shoe assembly has to be repaired or replaced at substantial expense not to mention the time that the street sweeper is kept out of service. In addition, in some situations the damage to the frame structure is so extensive that the actual frame structure of the street sweeper has to be repaired.
In the past, there have been interconnecting linkage systems provided that are designed with built in slop that enables the drag shoe to move to some degree laterally back and forth. For example, one is referred to the disclosure found in U.S. Pat. No. 4,557,010. There the drag shoe is supported by a series of rigid "z" bars that are connected between the frame structure of the street sweeper and drag shoe such that the actual connections incorporate slop to allow the drag shoe to move slightly laterally in response to an obstruction. But the drawback to this design is that the interconnecting links are still very rigid. As a result, the drag shoe can not withstand a substantial impact with a lateral obstruction during a turning maneuver, for example, without resulting in substantial damage to the drag shoe and the frame structure of the street sweeper.
Therefore, there is and continues to be a need for a drag shoe assembly for a street sweeper that will withstand substantial lateral impacts with obstructions such as manhole covers which will not result in significant damage to the drag shoe nor to the frame structure of the street sweeper.